A conventional shock absorbing apparatus will now be described with reference to the drawings. FIG. 18 is a central cross sectional view which illustrates a conventional single-type shock absorbing apparatus which has a body including a cylindrical portion formed therein, the cylindrical portion including a piston 202 integrally formed with a rod 201 and arranged slidably in a direction designated by arrows. On the other hand, the piston 202 has an orifice hole 203 bored therein so as to cause an enclosed operating fluid 204 to pass through the orifice hole 203. As a result, shocks can be absorbed.
As shown in FIGS. 19A and 19B, a structure for use in, for example, rotation drive unit has been known. The rotation drive unit has a rack b formed on one side surface of a drive piston a which gives rotational force to a rotational member (omitted from illustration). On the other hand, a drive shaft c, which is connected to the rotational member, has a pinion gear d engaged to the rack b. In a state where the aforesaid two elements are engaged to each other, compressed air serving as drive fluid, is introduced into a drive cylinder chamber e which accommodates the drive piston a, causing the drive piston a to be moved in the drive cylinder chamber 4. The movement of the drive piston e is, as rotational force, transmitted to the drive shaft c via the engaged rack b and the pinion gear d. As a result, the rotational member can be rotated.
In the aforesaid conventional structure, the range in which the rotational member is rotated, that is the range in which the drive shaft c is rotated is defined by a structure arranged in such a way that a piston f individually formed from the drive piston a and moving in synchronization with the drive piston a is slidably provided in a cylinder chamber g, a rack h formed on the piston f and the pinion gear d of the drive shaft c are engaged to each other. As a result, the two end portions of the rotational range of the rotational member are respectively defined at the two end portions of the movement range of the piston f. Therefore, stopper members i must be used in order to accurately stop the piston f at the aforesaid two end portions of the movement range of the piston f. Furthermore, shock absorbing apparatuses j must be provided at the two end portions of the cylinder chamber g in order to absorb the shock generated at the time of stopping the piston f before the stopper member i comes in contact with the stopper member i and stops there.
However, since the aforesaid conventional shock absorbing apparatus is able to absorb only one directional shock, two shock absorbing apparatuses must be disposed at the two end portions of the reciprocating motion in order to absorb the shock of a reciprocating movable body. Therefore, a problem arises in that the size of the apparatus cannot be reduced. Furthermore, if a function of adjusting the quantity of the shock absorption is further provided, the size of the apparatus becomes too large and the weight increases excessively.
The rotation drive unit which uses, for example, an air cylinder, as its power source, must be quickly stopped after it has performed the rotational operation. In order to rotate it in the two directions around the shaft, two shock absorbing apparatuses must be used. Therefore, the size and the cost of the rotation drive unit cannot be reduced.